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Règne :
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Animalia
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Embranchement :
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Chordata
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Classe :
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Elasmobranchii
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Ordre :
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Carcharhiniformes
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Famille :
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Carcharhinidae
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Genre :
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Carcharhinus
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Espèce :
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obscurus
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| Nom Français : |
Requin sombre.
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| Nom Vernaculaire : |
Dusky shark
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Description :
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The combination of characters that place the dusky shark among the western Atlantic members of its genus are: Trunk about one-fifth as high at first dorsal fin as it is long to origin of the caudal fin, tapering both forward and rearward; snout broadly rounded in front, its length in front of the nostrils less than the distance between the nostrils; the front edge of the nostril is not expanded as a definite lobe; the midline of the back between the two dorsal fins has a low but definite ridge, a character which is very precise, though seemingly minor; the first dorsal fin is considerably smaller than in the brown shark [page 42] (p. 43), with more deeply concave rear margin, its point of origin about over the inner corner of the pectoral (over the armpit of the pectoral in the brown shark); its apex is narrowly rounded. The free rear corner of the second dorsal fin is less than twice as long as the vertical height of the fin. The anal fin is a little longer, along the base, than the second dorsal and stands about under the latter. The caudal fin occupies between one-quarter and one-third of the total length of the shark, the lower caudal lobe (measured along its anterior edge) is about two-fifths as long as the upper lobe; and the upper lobe is noticeably slender toward its tip. The pectorals are about as long (from origin to tip) as the distance from the tip of the snout to the level of the first pair of gill openings, usually narrower, relatively, than in the brown shark, and sometimes more definitely sickle-shaped.
The upper teeth are broadly triangular; nearly erect toward the center of the mouth but weakly oblique toward its corners; their inner margins are nearly straight, the outer margins increasingly concave outward along the jaw. The lower teeth are erect, symmetrical, with narrow cusp on a broadly expanded base. Both the upper teeth and the lower are serrate along the edges, the lower the more finely so.
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Auteurs & dates :
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Carcharhinus obscurus (Lesueur, 1818)
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Recherche des images :
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Photo
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